The present inventive disclosure concerns a filter device for cleaning liquids in a motor vehicle, for example, separated diesel water of fuel filters including a porous ceramic support body.
A prior art filter device of this type is disclosed in DE 197 31 551 A1. The employed ceramic structures of the support body have a high strength but are comparatively brittle, i.e., inelastic. The ceramic filter membranes are porous structures with a high open pore volume (in general >30% open porosity). When water penetrates into these pores and freezes a partially very high stress is produced as a result of the volume expansion of water (up to 10%) which may cause destruction of the brittle ceramic. In order to prevent this or in order to relieve the ceramic structure, it is beneficial to reduce the dead volume in a way that the filter membrane is flowed through from the interior to the exterior because in this way the freezing water can expand through the membrane pores into an outwardly open environment. This configuration contributes significantly to improved freeze resistance. Such a measure alone is however not sufficient in order to ensure freeze-safe operation of the filter device.